What’s the relationship between brain chemicals and depression?

Important brain pathways are made up of chains of brain cells that conduct signals from one to another by releasing neurochemicals (serotonin, norepinephrine, or dopamine). These chains of brain cells carry signals to the target areas of your brain that turn on and off your alertness, anger, anxiety, appetite, energy, irritability, sadness, sleep, thoughts, and the physical workings of your body. If cells in the chain are damaged by depression, then the pathway is interrupted, and the signal never arrives at its destination, causing a disturbance in your emotions, behavior, and body processes. Adding additional serotonin, norepinephrine, and dopamine to the gaps between the cells makes it easier for damaged cells to pass signals down the chain so that the pathway is not interrupted. All antidepressants add serotonin, norepinephrine, or dopamine to the gaps between brain cells.